I will admit before today I had no idea what a caron or breve was. Doing some work on the next version of Hanzi Warrior I had the luxury of finding out. In doing an audit of the internal wordlists it appears that sometimes I found a caron and sometimes a breve for representing the third tone. In Unicode there is no u with both diaeresis and breve, therefore I converted all breves to carons with a little one-line sed script:
Here’s a handy little chart for future reference:
Although I still do not really know what the difference is, it does seem that one is more pointy than the other. Until someone gets the Unicode consortium to add a diaeresis/breve combo I suppose carons will rule the day. Does anyone have any preferences? Do you secretly use breves for Pinyin?